1. Field of the Invention
The present invention relates to an image sensor module and a camera module package having the same, which are used in mobile equipments or various monitoring devices. The image sensor module and the camera module package can be applied when bumps of an image sensor such as a complementary metal oxide semiconductor (CMOS) and an image sensor module board are directly connected to each other by using non-conductive paste (NCP).
2. Description of the Related Art
As the information communication technology rapidly develops, data communication speed is improved, and an amount of data communication is expanded. Further, an imaging device such as a CCD image sensor or CMOS image sensor is mounted on mobile electronic equipments such as mobile phones or notebooks, and thus image data as well as text data can be transmitted in real-time, the image data being taken by a camera module.
As for a method of packaging an image sensor for camera, there are provided a flip-chip COF (Chip On Film) method, a wire-bonding COB (Chip On Board) method, and a CSP (Chip Scale Package) method, among which the COF method and the COB method are widely used.
The COB method is a similar process to that of an existing semiconductor production line and has higher productivity than other packaging methods. However, since wire should be used for the connection with a PCB, the size of a module increases and an additional process is needed. Therefore, a new packaging technique is required to reduce the size of chip, to enhance heat dissipation and electrical performance, and to improve reliability. Accordingly, a COF method has emerged based on bumps having an external bonding projection.
In the COF method, a space for attaching wire is not needed. Therefore, the area of a package and the height of a lens barrel can be reduced. Further, since a thin film or flexible printed circuit board (FPCB) is used in the COF method, a reliable package which endures an external impact can be manufactured and the process thereof is relatively simplified. Moreover, the COF method satisfies such a tendency that signals are processed at high speed, high density is required, and multiple pins are needed.
Further, in a module using a mega-quality sensor to which various functions are added, the miniaturization of module, which has been a merit of the COF method, is not realized any more, because of the one-story structure thereof. The module cannot but be designed to have a larger size than in the COB method.
Currently, a double-sided flexible printed circuit board (FPCB) is used so that a module can be designed to have a similar size to that in the COB method, which does not satisfy the miniaturization of module which is a merit of the COF method. Therefore, since the COB method tends to be frequently used, the design and process technique for realizing the miniaturization of module are required.
Now, a conventional image sensor module using the COF method and a method of manufacturing the same will be described with reference to accompanying drawings, and the problems thereof will be examined.
FIG. 1 is a plan view illustrating the conventional image sensor module using the COF method.
As shown in FIG. 1, the image sensor module 30 includes an image sensor 33 which picks up an image to process into an electrical signal and a flexible printed circuit board (FPCB) 31 which is attached to the image sensor 33 so as to deliver a signal to the outside.
The image sensor 33 includes a pixel region (light receiving section) picking up an image from light incident from the outside and a signal processing region (ISP) having pads 34 formed on the outer portion of the image sensor so as to process an electrical signal with respect to the image picked up by the pixel region.
The FPCB 31 has a window 32 formed to have such a predetermined size that light received from a condensing lens of a lens section mounted on a housing passes through the window 32 so as to reach the image sensor 33.
The image sensor 33 is attached on the rear surface of the FPCB 31 by a flip-chip bonding method. The flip-chip bonding method is roughly classified into an ACF process and an NCP process. In the ACF process, an anisotropic conductive film (ACF) is inserted between the rear surface of the FPCB 31 and bumps projecting on the pads of the image sensor 33 and is then pressed so as to be attached. In the NCP process, non-conductive paste (NCP) is put between the rear surface of the FPCB 31 and the bumps projecting on the pads of the image sensor 33 and is then pressed so as to be attached. Through the flip-chip bonding method, a element-side electrode pads formed in the image sensor 33 are electrically connected to board-side electrode pads formed on the FPCB 31, and an electrical signal is delivered to an external mother board or the like via the circuit pattern 35 formed on the FPCB 31. Then, the image sensor module 30 coupled to the housing having the lens section is completed.
The flip-chip bonding method, in which the image sensor 33 is attached on the rear surface of the FPCB 31, will be described concretely.
In the ACF process in which such processes as shown in FIG. 2 are performed, an anisotropic conductive film of which the center portion is perforated to a predetermined size is aligned on the portion where the board-side pads are positioned. Then, pre-compression is performed so as to attach the film and the board.
Next, the image sensor having conductive bumps formed of silver or the like is positioned so as to correspond to the circumference of the film.
Next, the image sensor is heated at predetermined temperature so as to be pressed and attached on the board, so that the bumps formed in the image sensor and the pads formed on the board are connected to each other in a circuit manner.
Next, the peripheral portion of the image sensor is side-filled with resin or the like. Finally, a curing process is performed to complete manufacturing the image sensor module.
In the NCP process in which such processes as shown in FIG. 3 are performed, an image sensor having conductive bumps formed of silver or the like is first prepared.
Next, on a board having board-side pads formed, non-conductive paste (NCP) is dispensed in such a rectangular shape as to cover the pads.
Next, the image sensor having the conductive bumps formed thereon is positioned on the board on which the NCP is dispensed.
Finally, the image sensor having the conductive bumps formed thereon is heated and pressed, so that the bumps formed on the image sensor and the pads formed on the board are connected to each other in a circuit manner. Then, the board and the image sensor are pressed so as to be attached to each other, thereby completing manufacturing the image sensor module.
In the above-described COF packaging method, when the non-conductive paste of the NCP process is used instead of the anisotropic conductive film of the ACF process, a material cost can be reduced, and high durability against an external condition is provided to secure a highly reliable quality.
In spite of such advantages of the NCP process, the following problem occurs. When an image sensor is pressed and attached by a bonding device after non-conductive paste used as paste when the NCP process is applied is quantitatively coated on a board, an overflow (portion A) of non-conductive paste occurs where liquid-state non-conductive paste is overflowed into the image sensor, as shown in FIG. 4. Such an overflow causes fatal defects in image formation of the completed image sensor module. FIG. 4 shows a photograph for explaining the problem occurring when the NCP process for the COF packaging method is performed.